Miss Ruggles mother, Dr Sue Hills, said she felt she had failed her daughter by encouraging her to see the good in everyone and suggesting she ignore Dhillon until he went away.

Lance Corporal Trimaan DhillonCredit:
North News / NNP

Dhillon, a signaller with 2 Scots, was on Wednesday given a life sentence and told he would serve at least 22 years in prison for a crime of "utter barbarism".

A two week trial had heard Dhillon had terrified Miss Ruggles with a campaign of stalking, but she had told police she did not want him arrested.

One of Dhillon’s prior girlfriends had resorted to a restraining order against him because of his violence, the court heard.

Dr Hills, a maths teacher at a girls’ independent school, told Newcastle Crown Court: “I have always believed in looking for the good in everyone, I have taught that to my own children and my pupils.

Alice Ruggles was killed in her Gateshead flat

"I am now questioning whether this was right as it now appears to have led to my daughter being murdered.

"I am haunted by Alice saying she did not want to get Trimaan into trouble, she just wanted him to leave her alone.

"I will never forgive myself for advising her that if she ignored him he may leave her alone. I failed Alice in not advising her to stand up to Trimaan and that still haunts me."

Dhillon, 26, began to stalk Miss Ruggles after she ended their relationship because she discovered he had used internet dating apps to cheat on her.

She called Northumbria Police after Dhillon made a 250 mile round trip from his barracks in Scotland to tap at her bedroom window and place flowers and chocolates on the sill late at night.

He was given a Police Information Notice warning him to stay away from her and she was told to ring the officers if he made further contact.

But he continued and sent a package days later containing a note, photographs and a notebook.

When she called officers, they asked if she wanted him arrested, but the court heard she did not want to get him in trouble.

However she was angry about the police's lack of action, telling her sister, Emma: "They will f***ing respond once he has f***ing stabbed me."

Five days later he broke into her flat, cornered her in the bathroom and slit her throat.

Judge Paul Sloan QC told Dhillon: “Not a shred of remorse have you shown from first to last, indeed you were concentrating so hard on getting your story right when giving evidence, you forgot even to shed a crocodile tear."

After the sentence, Dr Hills said: “We believe there are important lessons to be learned from what happened to Alice. We didn't think that she was the sort of girl that something like this could happen to. We welcomed him into our family and he came across as a normal person. Unfortunately he was a cruel manipulative bully who made Alice miserable and took her away from us. With hindsight, there were many signs of stalking and coercive behaviour that we did not recognise. Everybody should know about these signs.”

The Independent Police Complaints Commission (IPCC) is currently looking at the force’s own internal investigation into what happened.

Det Ch Insp Lisa Theaker, of Northumbria Police, said at the time no one knew the threat Dhillon posed.

She said: “Alice didn't fully understand his level of behaviour and the stalking and the lengths of behaviour he was going to," she said.

"The family and the friends won't have fully understood it either.

"Alice spoke to a number of police officers and she spoke to Victims First and we went through a risk assessment.

"And as a result of that we would not have been able to predict at that stage that he would go on to murder Alice."

An IPCC spokeswoman said: "We received a referral, from Northumbria Police, regarding contact with Alice Ruggles before her death, and on the information received at that time the decision was taken that this should be investigated by the force.

"We have a copy of the force’s final investigation report which is now being reviewed, as is the normal process in such cases."